Re: Return value of pg_promote()

On Wed, Jun 7, 2023 at 9:55 PM Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
>
>
>
> On 2023/06/07 2:00, Laurenz Albe wrote:
> > On Tue, 2023-06-06 at 16:35 +0530, Ashutosh Sharma wrote:
> >> At present, pg_promote() returns true to the caller on successful
> >> promotion of standby, however it returns false in multiple scenarios
> >> which includes:
> >>
> >> 1) The SIGUSR1 signal could not be sent to the postmaster process.
> >> 2) The postmaster died during standby promotion.
> >> 3) Standby couldn't be promoted within the specified wait time.
> >>
> >> For an application calling this function, if pg_promote returns false,
> >> it is hard to interpret the reason behind it. So I think we should
> >> *only* allow pg_promote to return false when the server could not be
> >> promoted in the given wait time and in other scenarios it should just
> >> throw an error (FATAL, ERROR ... depending on the type of failure that
> >> occurred). Please let me know your thoughts on this change. thanks.!
> >
> > As the original author, I'd say that that sounds reasonable, particularly
> > in case #1. If the postmaster dies, we are going to die too, so it
> > probably doesn't matter much. But I think an error is certainly also
> > correct in that case.
>
> +1
>

Thanks for sharing your thoughts, Laurenz and Fujii-san. I've prepared
a patch that makes pg_promote error out if it couldn't send SIGUSR1 to
the postmaster or if the postmaster died in the middle of standby
promotion. PFA. Please note that now (with this patch) pg_promote only
returns false if the standby could not be promoted within the given
wait time. In case of any kind of failure, it just reports an error
based on the type of failure that occurred.

--
With Regards,
Ashutosh Sharma.